The Oceans and Global Warming

Currents Distributing Heat

Another important role the oceans play is that of distributor. Oceans deliver heat and life-sustaining nutrients around the globe.

Just as blood vessels and capillaries bring oxygen and nutrients to cells in the human body, the ocean's currents carry oxygen, nutrients and heat throughout the Earth. The ocean distributes 25 to 50 percent of the energy the planet receives from the sun.

For example, the Gulf Stream carries heat across the Atlantic. This warm current gives northwestern Europe a milder climate than it would normally have so far north.

A change to the ocean's circulation patterns could plunge Europe into a colder era, even as the rest of world experiences warmer temperatures. (Find out more about the ocean's circulation system on oceansalive.org.)

Currents Circulating Food

Changing ocean circulation patterns would also affect the nutrient delivery system for marine life. Colder waters are more productive than warm waters. The warming of the oceans may be starting to break the ocean's food chain.

The system of currents replenishes deep waters with oxygen and carries nutrients to surface waters where microscopic plants known as phytoplankton can use them. When cold, nutrient-rich waters rise to the surface seasonally and mix with sunlit surface waters, the upwellings trigger the growth of phytoplankton.

The areas where these upwellings occur are often rich fishing grounds, the sea's "gardens of Eden" where an abundance of marine life flourishes.

As oceans absorb more heat, upwellings of cold, nutrient-rich waters can become less frequent. Without this nourishment, blooms of plant plankton, which are the base of the marine food chain, are disrupted and so food for sea life up the food chain, like krill, larger fish and seabirds, is cut off.

To make things worse, phytoplankton use carbon dioxide for photosynthesis. With fewer plankton, the oceans could not remove as much carbon dioxide from the atmosphere.